1. Field of the Invention
The present invention relates to a vehicle motion control device for controlling a motion of a vehicle by controlling braking force exerted on each wheel of the vehicle.
2. Description of the Prior Arts
There has conventionally been a demand for controlling a vehicle motion so as to prevent the turning state of the vehicle from being unstable due to the occurrence of an excessive roll angle on the vehicle, when the vehicle is in the turning state. This roll angle depends generally upon the magnitude of an actual lateral acceleration (accordingly, the centrifugal force exerted on the vehicle) that is a component of an acceleration actually exerted on the vehicle in the side-to-side direction of the vehicle body, and increases with the increase of the actual lateral acceleration. On the other hand, the magnitude of the actual lateral acceleration exerted on the vehicle is decreased by producing a yawing moment in the direction opposite to the turning direction of the vehicle or by decelerating the vehicle.
From the above, a vehicle motion control device disclosed in the patent document 1 executes a control for exerting predetermined braking force on the outer wheel in the turning direction of the vehicle when the actual lateral acceleration (its absolute value) exceeds a predetermined roll-over preventing threshold value with the vehicle brought into a turning state. According to this device, a yawing moment is given to the vehicle in the direction opposite to the turning direction of the vehicle due to the predetermined braking force, whereby the magnitude of the actual lateral acceleration exerted on the vehicle is decreased, thereby being capable of preventing the occurrence of the excessive roll angle on the vehicle.
[Patent Document 1]
Japanese Unexamined Patent Application No. HEI 10-81215
However, when the braking force is exerted on the outer wheel of the turning direction according to the above-mentioned device, a yawing moment is caused on the vehicle in the direction opposite to the turning direction of the vehicle, so that the turning state of the vehicle is controlled to be brought into an understeer state. Consequently, the turning radius of the vehicle becomes greater than the expected turning radius, thereby entailing a problem that there may be a case where a tracing performance cannot satisfactorily be maintained.